My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 feet
of wire.
What I am trying now is W8JI suggested modification design to improve the
ATR-10 design by taps on the coil for adjustment. Works well.
http://www.w8ji.com/antenna_tuners.htm
Had my MFJ-989B at the feed point, I had to add a capacitor to ground 250pf
so it could work. Inductance was at max farthest away from ground. Voltage
was so high at 300 watts in, the 0.125 meshed plate spacing arced over, it
has a T network and I had expected this to happen.
http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500
watts.
What I was looking at is removing the coil and the input would be at the
top of C1. I made a test with QRP using 2 small spaced caps taken out of an
MFJ-901A. Works well. Because of the high voltage situation would there be
an issue with this and I need to go to a 0.25 inch spacing between plates?
Vacuum variables are out of my price range.
ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of
the coil would make this a low pass circuit. Besides that on 160M which one
would be more efficient, and off the top of your head what would be the
percentages? If you had my make do with what I have setup, what tuning
network would you use?
Does any one have an email address for MFJ Service department? I have the
wrong one. I sent my MFJ 998RT to their Service department, the High
voltage that was developed with 300 watts pretty much done it in. The
ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing
with out the inductor.
--
Jim K9TF
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Topband Reflector
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